Using (1) longevity, (2) causes of death, (3) the age of retirement, (4) the completeness of retirement, (5) retirement benefits, (6) the filing of a claim for disability benefits, (7) causes of disability, (8) the granting or the denial or disability benefits, (9) the duration of disability benefit payments, (10) the mode of termination of disability benefits, and (11) the lifetime covered earning gradient as criteria of health to determine whether exposure to external and/or internal radiation, received at Hanford or at other atomic plants, or other industrial hazards while working at Hanford, had adverse effect on employee health. It is a longitudinal study consisting of 35,000 Hanford employees, at least 80 percent of whom have had exposure to radiation of varying dose levels and length of time; 20,000 identified siblings of Hanford employees of the same sex; and 35,000 controls matched to each employee, taken from the Social Security Administration's one percent Continuous Work History Sample. It extends over the years 1943-72, representing some two million man-years of observations. Hanford has detailed records of annual external and internal radiation exposure for all of its employees, and exposure to other industrial hazards while employed at Hanford; we have supplementary information on radiation exposure of Hanford employees received in other atomic plants. Other than causes of death, which would be obtained from death certificates, all information will come from the files of SSA.